function siteTime() {
    window.setTimeout("siteTime()", 1000);
    var seconds = 1000;
    var minutes = seconds * 60;
    var hours = minutes * 60;
    var days = hours * 24;
    var years = days * 365;
    var today = new Date();
    var todayYear = today.getFullYear();
    var todayMonth = today.getMonth() + 1;
    var todayDate = today.getDate();
    var todayHour = today.getHours();
    var todayMinute = today.getMinutes();
    var todaySecond = today.getSeconds();
    var t1 = Date.UTC(2019, 04, 20, 00, 00, 00); //北京时间
    var t2 = Date.UTC(todayYear, todayMonth, todayDate, todayHour, todayMinute, todaySecond);
    var diff = t2 - t1;
    var diffYears = Math.floor(diff / years);
    var diffDays = Math.floor((diff / days) - diffYears * 365);
    var diffHours = Math.floor((diff - (diffYears * 365 + diffDays) * days) / hours);
    var diffMinutes = Math.floor((diff - (diffYears * 365 + diffDays) * days - diffHours * hours) / minutes);
    var diffSeconds = Math.floor((diff - (diffYears * 365 + diffDays) * days - diffHours * hours - diffMinutes * minutes) / seconds);
    document.getElementById("sitetime").innerHTML = diffYears + "年" + diffDays + "天" + diffHours + "时" + diffMinutes + "分" + diffSeconds + "秒";
}
siteTime();